1. Field of the Invention
This invention relates generally to configurable power tank for power delivery and storage and, more particularly, to a plurality of supercapacitor elements arranged in rows and columns in a single housing with an integrated configuration circuit. The latter can configure the elements in real-time responses to fulfill power demands and to save recoverable power.
2. Description of the Related Art
Energy efficiency is a crucial issue, especially, in the era of high oil prices and quick depletion of petroleum depositories. Industries from automobile and electric locomotive to semiconductor to utility have dedicated a lot of resources to improve the energy efficiency of manufacturing processes and products. Due to the assistance of batteries, the hybrid cars generate better energy efficiency and gas mileage than the comparable regular gas models. One of the gas-saving factors of hybrids is that the battery can be used to retrieve the residual energy of the vehicles in regenerative braking. There is no such energy recovering capability in the regular gasoline cars. However, all batteries rely on specific chemical reactions for energy delivery and energy storage known as discharging and charging, respectively. The kinetic and thermodynamic characteristics of the foregoing energy conversions often restrict the power capacity, charge and discharge efficiency, as well as lifetime of batteries. In power delivery and storage for high-power applications, batteries are inadequate because of the chemical nature.
Energy in the form of electricity is directly stored and released in capacitors via various physical processes. Among them, surface adsorption and de-sorption are the mechanisms of energy storage and energy delivery, respectively, for electrolytic capacitors. The electrodes of the capacitors adsorb ions from an electrolyte at charging, while the stored energy is delivered with automatic de-sorption of ions at discharging. Due to the complete reversibility and fast response of physical processes, the capacitors have long life, high power density, as well as good energy efficiency at charging and discharging. Assuming the unique properties of an electrolytic capacitor, the supercapacitor advances the application of capacitor to a higher level of power provision by offering hundreds to thousands times more energy content of those of conventional capacitors.
Though the energy content of today's supercapacitor is still no match to the battery, the former is used to improve the power density and lifetime of battery. The foregoing enhancement of battery power and lifetime is known as the load leveling effect. Numerous applications of the load leveling effect have been patented, for example, U.S. Pat. Nos. 5,146,095; 5,545,933; 5,604,426; 5,663,628; 5,734,205; 6,995,480 and 7,002,112, just to name a few.
In all previous work with supercapacitor-related applications, the capacitor can only provide one delivery of one peak power. Then the capacitor requires a refill of energy for the second round of power provision. As shown in FIG. 1, the supercapacitor may discharge from Vs, the fully charged level ST, to 0 volts. Then, it may take a period from T1 to T2 for refilling the capacitor to Vs for delivering power again. Thus, the power delivery of the conventional use of supercapacitor is intermittent. Such power outrage is clearly unacceptable to many high-power applications.
Furthermore, as the voltage of the supercapacitor drops below the threshold voltage level TH to drive a load, the residual energy of the capacitor becomes ineffective due to insufficient driving force. This ineffective energy will be discharged and refilled without contribution to the work of the capacitor. In the repetitive charge and discharge of supercapacitor, a great amount of energy is wasted. To compensate the ineffective energy, supercapacitor is commonly over-designed for power applications resulting in high cost. This, in turn, is why it needs a method to improve its power management more efficiently and economically. Another problem in the use of supercapacitor is that many well-packaged capacitors are connected in series for producing the needed output voltages. When the module is charged or discharged in series, there is always an imbalance of voltage distribution among the members in the pack. To overcome the uneven distribution of voltage, each capacitor is assigned a protection circuit. Henceforth, an effective and economical method of cell assembly of the power tank supercapacitor modules for the power applications is needed as well.